Reducing the amount of starch fed to fresh dairy cows may improve early lactation milk production in some scenarios, say researchers at the Miner Institute, Chazy, NY.
They point out that controlled-energy diets are recommended for use in the far-off dry period in one- or two-group management systems. That approach has been successful in some but not all dairies, and they think some of the failures may be attributed to a transition to an inappropriate fresh-cow diet.
Seventy-two Holstein cows were used to evaluate the effect of starch content in corn silage-based diets on early lactation performance following a shortened (40-day) dry period when a controlled-energy diet was fed. The scientists point out that controlled-energy dry-cow diets typically contain 12-16% starch on a dry matter basis, much less than lactation diets. A phase feeding or step-up approach during the pre- and post-freshening periods is often recommended, but the optimal increase in starch from a controlled-energy dry diet to a lactation diet is unknown.
Treatments included a low-starch diet (21.0%) for the first 91 days in milk, a medium-starch diet (23.2%) for the first 21 days in milk followed by a high-starch diet (25.5%) for the next 70 days, and a high-starch diet (25.5%) for the first 91 days. Corn meal was replaced partially with soy hulls and wheat middlings in the low- and medium-starch diets.
Cows fed the low-starch diet for the 91 days tended to consume more dry matter and produce more milk than did the high-starch group. Those fed a medium-starch diet for 21 days followed by a high-starch diet for 70 days outperformed cows fed the high-starch ration throughout the trial. That shows the benefit of using a step-up starch feeding approach when a controlled-energy dry-cow diet is fed, say the researchers.